Homework Help:
Two problems i just can't get please help

A playground carousel is free to rotate about its center on frictionless bearings, and air resistance is negligible. The carousel itself (without riders) has a moment of inertia of 120 kgm2. When one person is standing at a distance of 1.40 m from the center, the carousel has an angular velocity of 0.500 rad/s. However, as this person moves inward to a point located 0.740 m from the center, the angular velocity increases to 0.640 rad/s. What is the person's mass?

A wrecking ball (weight = 4500 N) is supported by a boom, which may be assumed to be uniform and has a weight of 3100 N. As the drawing shows, a support cable runs from the top of the boom to the tractor. The angle between the support cable and the horizontal is 32°, and the angle between the boom and the horizontal is 48°.
(a) Find the tension in the support cable.

(b) Find the magnitude of the force exerted on the lower end of the boom by the hinge at point P.

Sorry about that I thought I did use the hw thread. For the first problem I did WI=I1W1+I2W2 and so with the number is would look like this (120)(.5)=(120+m0.740 squared)(.640) ...i know I is mrsquared.
For the seconde I drew all the forces as included in the link above when someone else had this problem but didn't know how to set up the equation to slove for the answers.

Sorry about that I thought I did use the hw thread. For the first problem I did WI=I1W1+I2W2 and so with the number is would look like this (120)(.5)=(120+m0.740 squared)(.640) ...i know I is mrsquared.

You applied something on the right hand side of the red equation that you didn't apply on the left hand side. Do so, and you should obtain the correct answer.

Staff: Mentor

For this question, u may need to use the equations
[tex]\sum F_x = 0 , \sum F_y = 0 and \sum \tau = 0 [/tex].
Let the tension in the support cable be T and the normal reaction force at P be R.
Then, using [tex]\sum F_y = 0 [/tex], u'll get T sin 32 + R sin 48 - 4500 - 3100 = 0.
Using [tex]\sum F_x = 0 [/tex], u'll get T cos 32 + R cos 48 = 0.
Solve the 2 equations simultaneously and u can get the values of T and R. T is needed for part (a) while R is needed for part (b).

Hope that helps.

NTUENG, We appreciate your helping out with homework questions, but please avoid doing a lot of the OP's work for them. In your post above, it would have been better for you to ask more tutorial questions, rather than doing the math for the component forces for the student. Your intentions are good, but you need to understand that doing the work for the student does not help them learn as much as guiding them towards discovering out how to do the work.